// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

namespace System.Data.Entity.Core.Mapping.Update.Internal
{
    using System.Data.Entity.Core.Common;
    using System.Data.Entity.Core.Metadata.Edm;
    using System.Data.Entity.Core.Objects;
    using System.Data.Entity.Resources;
    using System.Data.Entity.Utilities;
    using System.Diagnostics;
    using System.Diagnostics.CodeAnalysis;
    using System.Globalization;
    using System.Linq;
    using System.Text;

    // <summary>
    // requires: for structural types, member values are ordinally aligned with the members of the
    // structural type.
    // Stores a 'row' (or element within a row) being propagated through the update pipeline, including
    // markup information and metadata. Internally, we maintain several different classes so that we only
    // store the necessary state.
    // - StructuralValue (complex types, entities, and association end keys): type and member values,
    // one version for modified structural values and one version for unmodified structural values
    // (a structural type is modified if its _type_ is changed, not its values
    // - SimpleValue (scalar value): flags to describe the state of the value (is it a concurrency value,
    // is it modified) and the value itself
    // - ServerGenSimpleValue: adds back-prop information to the above (record and position in record
    // so that we can set the value on back-prop)
    // - KeyValue: the originating IEntityStateEntry also travels with keys. These entries are used purely for
    // error reporting. We send them with keys so that every row containing an entity (which must also
    // contain the key) has enough context to recover the state entry.
    // </summary>
    // <remarks>
    // Not all members of a PropagatorResult are available for all specializations. For instance, GetSimpleValue
    // is available only on simple types
    // </remarks>
    internal abstract class PropagatorResult
    {
        #region Constructors

        // For testing purposes. Only nested classes should derive from propagator result

        #endregion

        #region Fields

        internal const int NullIdentifier = -1;
        internal const int NullOrdinal = -1;

        #endregion

        #region Properties

        // <summary>
        // Gets a value indicating whether this result is null.
        // </summary>
        internal abstract bool IsNull { get; }

        // <summary>
        // Gets a value indicating whether this is a simple (scalar) or complex
        // structural) result.
        // </summary>
        internal abstract bool IsSimple { get; }

        // <summary>
        // Gets flags describing the behaviors for this element.
        // </summary>
        internal virtual PropagatorFlags PropagatorFlags
        {
            get { return PropagatorFlags.NoFlags; }
        }

        // <summary>
        // Gets all state entries from which this result originated. Only set for key
        // values (to ensure every row knows all of its source entries)
        // </summary>
        internal virtual IEntityStateEntry StateEntry
        {
            get { return null; }
        }

        // <summary>
        // Gets record from which this result originated. Only set for server generated
        // results (where the record needs to be synchronized).
        // </summary>
        internal virtual CurrentValueRecord Record
        {
            get { return null; }
        }

        // <summary>
        // Gets structural type for non simple results. Only available for entity and complex type
        // results.
        // </summary>
        internal virtual StructuralType StructuralType
        {
            get { return null; }
        }

        // <summary>
        // Gets the ordinal within the originating record for this result. Only set
        // for server generated results (otherwise, returns -1)
        // </summary>
        internal virtual int RecordOrdinal
        {
            get { return NullOrdinal; }
        }

        // <summary>
        // Gets the identifier for this entry if it is a server-gen key value (otherwise
        // returns -1)
        // </summary>
        internal virtual int Identifier
        {
            get { return NullIdentifier; }
        }

        // <summary>
        // Where a single result corresponds to multiple key inputs, they are chained using this linked list.
        // By convention, the first entry in the chain is the 'dominant' entry (the principal key).
        // </summary>
        internal virtual PropagatorResult Next
        {
            get { return null; }
        }

        #endregion

        #region Methods

        // <summary>
        // Returns simple value stored in this result. Only valid when <see cref="IsSimple" /> is
        // true.
        // </summary>
        // <returns> Concrete value. </returns>
        internal virtual object GetSimpleValue()
        {
            throw EntityUtil.InternalError(
                EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "PropagatorResult.GetSimpleValue");
        }

        // <summary>
        // Returns nested value. Only valid when <see cref="IsSimple" /> is false.
        // </summary>
        // <param name="ordinal"> Ordinal of value to return (ordinal based on type definition) </param>
        // <returns> Nested result. </returns>
        internal virtual PropagatorResult GetMemberValue(int ordinal)
        {
            throw EntityUtil.InternalError(
                EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "PropagatorResult.GetMemberValue");
        }

        // <summary>
        // Returns nested value. Only valid when <see cref="IsSimple" /> is false.
        // </summary>
        // <param name="member"> Member for which to return a value </param>
        // <returns> Nested result. </returns>
        internal PropagatorResult GetMemberValue(EdmMember member)
        {
            var ordinal = TypeHelpers.GetAllStructuralMembers(StructuralType).IndexOf(member);
            return GetMemberValue(ordinal);
        }

        // <summary>
        // Returns all structural values. Only valid when <see cref="IsSimple" /> is false.
        // </summary>
        // <returns> Values of all structural members. </returns>
        internal virtual PropagatorResult[] GetMemberValues()
        {
            throw EntityUtil.InternalError(
                EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "PropagatorResult.GetMembersValues");
        }

        // <summary>
        // Produces a replica of this propagator result with different flags.
        // </summary>
        // <param name="flags"> New flags for the result. </param>
        // <returns> This result with the given flags. </returns>
        internal abstract PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags);

        // <summary>
        // Copies this result replacing its value. Used for cast. Requires a simple result.
        // </summary>
        // <param name="value"> New value for result </param>
        // <returns> Copy of this result with new value. </returns>
        internal virtual PropagatorResult ReplicateResultWithNewValue(object value)
        {
            throw EntityUtil.InternalError(
                EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "PropagatorResult.ReplicateResultWithNewValue");
        }

        // <summary>
        // Replaces parts of the structured result.
        // </summary>
        // <param name="map"> A replace-with map applied to simple (i.e. not structural) values. </param>
        // <returns> Result with requested elements replaced. </returns>
        internal abstract PropagatorResult Replace(Func<PropagatorResult, PropagatorResult> map);

        // <summary>
        // A result is merged with another when it is merged as part of an equi-join.
        // </summary>
        // <remarks>
        // In theory, this should only ever be called on two keys (since we only join on
        // keys). We throw in the base implementation, and override in KeyResult. By convention
        // the principal key is always the first result in the chain (in case of an RIC). In
        // addition, entity entries always appear before relationship entries.
        // </remarks>
        // <param name="other"> Result to merge with. </param>
        // <returns> Merged result. </returns>
        internal virtual PropagatorResult Merge(KeyManager keyManager, PropagatorResult other)
        {
            throw EntityUtil.InternalError(EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "PropagatorResult.Merge");
        }

        internal virtual void SetServerGenValue(object value)
        {
            if (RecordOrdinal != NullOrdinal)
            {
                var targetRecord = Record;

                // determine if type compensation is required
                IExtendedDataRecord recordWithMetadata = targetRecord;
                var member = recordWithMetadata.DataRecordInfo.FieldMetadata[RecordOrdinal].FieldType;

                value = value ?? DBNull.Value; // records expect DBNull rather than null
                value = AlignReturnValue(value, member);
                targetRecord.SetValue(RecordOrdinal, value);
            }
        }

        // <summary>
        // Aligns a value returned from the store with the expected type for the member.
        // </summary>
        // <param name="value"> Value to convert. </param>
        // <param name="member"> Metadata for the member being set. </param>
        // <returns> Converted return value </returns>
        internal object AlignReturnValue(object value, EdmMember member)
        {
            if (DBNull.Value.Equals(value))
            {
                // check if there is a nullability constraint on the value
                if (BuiltInTypeKind.EdmProperty == member.BuiltInTypeKind
                    &&
                    !((EdmProperty)member).Nullable)
                {
                    throw EntityUtil.Update(
                        Strings.Update_NullReturnValueForNonNullableMember(
                            member.Name,
                            member.DeclaringType.FullName), null);
                }
            }
            else if (!Helper.IsSpatialType(member.TypeUsage))
            {
                Type clrType;
                Type clrEnumType = null;
                if (Helper.IsEnumType(member.TypeUsage.EdmType))
                {
                    var underlyingType = Helper.AsPrimitive(member.TypeUsage.EdmType);
                    clrEnumType = Record.GetFieldType(RecordOrdinal);
                    clrType = underlyingType.ClrEquivalentType;
                    Debug.Assert(clrEnumType.IsEnum());
                }
                else
                {
                    // convert the value to the appropriate CLR type
                    Debug.Assert(
                        BuiltInTypeKind.PrimitiveType == member.TypeUsage.EdmType.BuiltInTypeKind,
                        "we only allow return values that are instances of EDM primitive or enum types");
                    var primitiveType = (PrimitiveType)member.TypeUsage.EdmType;
                    clrType = primitiveType.ClrEquivalentType;
                }

                try
                {
                    value = Convert.ChangeType(value, clrType, CultureInfo.InvariantCulture);
                    if (clrEnumType != null)
                    {
                        value = Enum.ToObject(clrEnumType, value);
                    }
                }
                catch (Exception e)
                {
                    // we should not be wrapping all exceptions
                    if (e.RequiresContext())
                    {
                        var userClrType = clrEnumType ?? clrType;
                        throw EntityUtil.Update(
                            Strings.Update_ReturnValueHasUnexpectedType(
                                value.GetType().FullName,
                                userClrType.FullName,
                                member.Name,
                                member.DeclaringType.FullName), e);
                    }
                    throw;
                }
            }

            // return the adjusted value
            return value;
        }

#if DEBUG
        public override string ToString()
        {
            var builder = new StringBuilder();
            if (PropagatorFlags.NoFlags != PropagatorFlags)
            {
                builder.Append(PropagatorFlags.ToString()).Append(":");
            }
            if (NullIdentifier != Identifier)
            {
                builder.Append("id").Append(Identifier.ToString(CultureInfo.InvariantCulture)).Append(":");
            }
            if (NullOrdinal != RecordOrdinal)
            {
                builder.Append("ord").Append(RecordOrdinal.ToString(CultureInfo.InvariantCulture)).Append(":");
            }
            if (IsSimple)
            {
                builder.AppendFormat(CultureInfo.InvariantCulture, "{0}", GetSimpleValue());
            }
            else
            {
                if (!Helper.IsRowType(StructuralType))
                {
                    builder.Append(StructuralType.Name).Append(":");
                }
                builder.Append("{");
                var first = true;
                foreach (var memberValue in Helper.PairEnumerations(
                    TypeHelpers.GetAllStructuralMembers(StructuralType), GetMemberValues()))
                {
                    if (first)
                    {
                        first = false;
                    }
                    else
                    {
                        builder.Append(", ");
                    }
                    builder.Append(memberValue.Key.Name).Append("=").Append(memberValue.Value);
                }
                builder.Append("}");
            }
            return builder.ToString();
        }
#endif

        #endregion

        #region Nested types and factory methods

        internal static PropagatorResult CreateSimpleValue(PropagatorFlags flags, object value)
        {
            return new SimpleValue(flags, value);
        }

        private class SimpleValue : PropagatorResult
        {
            internal SimpleValue(PropagatorFlags flags, object value)
            {
                m_flags = flags;
                m_value = value ?? DBNull.Value;
            }

            private readonly PropagatorFlags m_flags;
            protected readonly object m_value;

            internal override PropagatorFlags PropagatorFlags
            {
                get { return m_flags; }
            }

            internal override bool IsSimple
            {
                get { return true; }
            }

            internal override bool IsNull
            {
                get
                {
                    // The result is null if it is not associated with an identifier and
                    // the value provided by the user is also null.
                    return NullIdentifier == Identifier && DBNull.Value == m_value;
                }
            }

            internal override object GetSimpleValue()
            {
                return m_value;
            }

            internal override PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags)
            {
                return new SimpleValue(flags, m_value);
            }

            internal override PropagatorResult ReplicateResultWithNewValue(object value)
            {
                return new SimpleValue(PropagatorFlags, value);
            }

            internal override PropagatorResult Replace(Func<PropagatorResult, PropagatorResult> map)
            {
                return map(this);
            }
        }

        internal static PropagatorResult CreateServerGenSimpleValue(
            PropagatorFlags flags, object value, CurrentValueRecord record, int recordOrdinal)
        {
            return new ServerGenSimpleValue(flags, value, record, recordOrdinal);
        }

        private class ServerGenSimpleValue : SimpleValue
        {
            internal ServerGenSimpleValue(PropagatorFlags flags, object value, CurrentValueRecord record, int recordOrdinal)
                : base(flags, value)
            {
                DebugCheck.NotNull(record);

                m_record = record;
                m_recordOrdinal = recordOrdinal;
            }

            private readonly CurrentValueRecord m_record;
            private readonly int m_recordOrdinal;

            internal override CurrentValueRecord Record
            {
                get { return m_record; }
            }

            internal override int RecordOrdinal
            {
                get { return m_recordOrdinal; }
            }

            internal override PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags)
            {
                return new ServerGenSimpleValue(flags, m_value, Record, RecordOrdinal);
            }

            internal override PropagatorResult ReplicateResultWithNewValue(object value)
            {
                return new ServerGenSimpleValue(PropagatorFlags, value, Record, RecordOrdinal);
            }
        }

        internal static PropagatorResult CreateKeyValue(PropagatorFlags flags, object value, IEntityStateEntry stateEntry, int identifier)
        {
            return new KeyValue(flags, value, stateEntry, identifier, null);
        }

        private class KeyValue : SimpleValue
        {
            internal KeyValue(PropagatorFlags flags, object value, IEntityStateEntry stateEntry, int identifier, KeyValue next)
                : base(flags, value)
            {
                DebugCheck.NotNull(stateEntry);

                m_stateEntry = stateEntry;
                m_identifier = identifier;
                m_next = next;
            }

            private readonly IEntityStateEntry m_stateEntry;
            private readonly int m_identifier;
            protected readonly KeyValue m_next;

            internal override IEntityStateEntry StateEntry
            {
                get { return m_stateEntry; }
            }

            internal override int Identifier
            {
                get { return m_identifier; }
            }

            internal override CurrentValueRecord Record
            {
                get
                {
                    // delegate to the state entry, which also has the record
                    return m_stateEntry.CurrentValues;
                }
            }

            internal override PropagatorResult Next
            {
                get { return m_next; }
            }

            internal override PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags)
            {
                return new KeyValue(flags, m_value, StateEntry, Identifier, m_next);
            }

            internal override PropagatorResult ReplicateResultWithNewValue(object value)
            {
                return new KeyValue(PropagatorFlags, value, StateEntry, Identifier, m_next);
            }

            internal virtual KeyValue ReplicateResultWithNewNext(KeyValue next)
            {
                if (m_next != null)
                {
                    // push the next value to the end of the linked list
                    next = m_next.ReplicateResultWithNewNext(next);
                }
                return new KeyValue(PropagatorFlags, m_value, m_stateEntry, m_identifier, next);
            }

            internal override PropagatorResult Merge(KeyManager keyManager, PropagatorResult other)
            {
                var otherKey = other as KeyValue;
                if (null == otherKey)
                {
                    EntityUtil.InternalError(EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "KeyValue.Merge");
                }

                // Determine which key (this or otherKey) is first in the chain. Principal keys take
                // precedence over dependent keys and entities take precedence over relationships.
                if (Identifier != otherKey.Identifier)
                {
                    // Find principal (if any)
                    if (keyManager.GetPrincipals(otherKey.Identifier).Contains(Identifier))
                    {
                        return ReplicateResultWithNewNext(otherKey);
                    }
                    else
                    {
                        return otherKey.ReplicateResultWithNewNext(this);
                    }
                }
                else
                {
                    // Entity takes precedence of relationship
                    if (null == m_stateEntry
                        || m_stateEntry.IsRelationship)
                    {
                        return otherKey.ReplicateResultWithNewNext(this);
                    }
                    else
                    {
                        return ReplicateResultWithNewNext(otherKey);
                    }
                }
            }
        }

        internal static PropagatorResult CreateServerGenKeyValue(
            PropagatorFlags flags, object value, IEntityStateEntry stateEntry, int identifier, int recordOrdinal)
        {
            return new ServerGenKeyValue(flags, value, stateEntry, identifier, recordOrdinal, null);
        }

        private class ServerGenKeyValue : KeyValue
        {
            internal ServerGenKeyValue(
                PropagatorFlags flags, object value, IEntityStateEntry stateEntry, int identifier, int recordOrdinal, KeyValue next)
                : base(flags, value, stateEntry, identifier, next)
            {
                m_recordOrdinal = recordOrdinal;
            }

            private readonly int m_recordOrdinal;

            internal override int RecordOrdinal
            {
                get { return m_recordOrdinal; }
            }

            internal override PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags)
            {
                return new ServerGenKeyValue(flags, m_value, StateEntry, Identifier, RecordOrdinal, m_next);
            }

            internal override PropagatorResult ReplicateResultWithNewValue(object value)
            {
                return new ServerGenKeyValue(PropagatorFlags, value, StateEntry, Identifier, RecordOrdinal, m_next);
            }

            internal override KeyValue ReplicateResultWithNewNext(KeyValue next)
            {
                if (m_next != null)
                {
                    // push the next value to the end of the linked list
                    next = m_next.ReplicateResultWithNewNext(next);
                }
                return new ServerGenKeyValue(PropagatorFlags, m_value, StateEntry, Identifier, RecordOrdinal, next);
            }
        }

        internal static PropagatorResult CreateStructuralValue(PropagatorResult[] values, StructuralType structuralType, bool isModified)
        {
            if (isModified)
            {
                return new StructuralValue(values, structuralType);
            }
            else
            {
                return new UnmodifiedStructuralValue(values, structuralType);
            }
        }

        private class StructuralValue : PropagatorResult
        {
            internal StructuralValue(PropagatorResult[] values, StructuralType structuralType)
            {
                DebugCheck.NotNull(structuralType);
                DebugCheck.NotNull(values);
                Debug.Assert(values.Length == TypeHelpers.GetAllStructuralMembers(structuralType).Count);

                m_values = values;
                m_structuralType = structuralType;
            }

            private readonly PropagatorResult[] m_values;
            protected readonly StructuralType m_structuralType;

            internal override bool IsSimple
            {
                get { return false; }
            }

            internal override bool IsNull
            {
                get { return false; }
            }

            internal override StructuralType StructuralType
            {
                get { return m_structuralType; }
            }

            internal override PropagatorResult GetMemberValue(int ordinal)
            {
                return m_values[ordinal];
            }

            internal override PropagatorResult[] GetMemberValues()
            {
                return m_values;
            }

            internal override PropagatorResult ReplicateResultWithNewFlags(PropagatorFlags flags)
            {
                throw EntityUtil.InternalError(
                    EntityUtil.InternalErrorCode.UpdatePipelineResultRequestInvalid, 0, "StructuralValue.ReplicateResultWithNewFlags");
            }

            internal override PropagatorResult Replace(Func<PropagatorResult, PropagatorResult> map)
            {
                var newValues = ReplaceValues(map);
                return null == newValues ? this : new StructuralValue(newValues, m_structuralType);
            }

            protected PropagatorResult[] ReplaceValues(Func<PropagatorResult, PropagatorResult> map)
            {
                var newValues = new PropagatorResult[m_values.Length];
                var hasChange = false;
                for (var i = 0; i < newValues.Length; i++)
                {
                    var newValue = m_values[i].Replace(map);
                    if (!ReferenceEquals(newValue, m_values[i]))
                    {
                        hasChange = true;
                    }
                    newValues[i] = newValue;
                }
                return hasChange ? newValues : null;
            }
        }

        private class UnmodifiedStructuralValue : StructuralValue
        {
            internal UnmodifiedStructuralValue(PropagatorResult[] values, StructuralType structuralType)
                : base(values, structuralType)
            {
            }

            internal override PropagatorFlags PropagatorFlags
            {
                get { return PropagatorFlags.Preserve; }
            }

            internal override PropagatorResult Replace(Func<PropagatorResult, PropagatorResult> map)
            {
                var newValues = ReplaceValues(map);
                return null == newValues ? this : new UnmodifiedStructuralValue(newValues, m_structuralType);
            }
        }

        #endregion
    }
}
